Top menu in IE 9 in a new colibri skin looks invisible. Only ADD looks fine. It was reproduced on several computers.
Actually TOP MENU works fine, submenu work fine. My main problem was, that users couldn't find logout link.
TOP menu background doesn't work correctly also
(IT works correctly ONLY in compatibility mode in IE, so to reproduce the bug you need to turn compatibility view off in IE)
How to reproduce:
1. Set up clear installation (Windows standalone would be fine)
2. Log in as default Admin
4. Rights, set up as shown in screenshot (XWiki Preferences - Rights.png)
5. Logout, see correct Login screen
6. Login as default Admin
6. Watch results (XWiki IE bug.png)